Population fluctuations seen in the teredinid species settling in estuarine waters at Marshall Lagoon over a 3 year period were correlated with the salinity fluctuations to which they had been subjected. From these calculations the salinity range in which the most common species settled was determined. Studies in the aquarium were designed to test the salinity range of these teredinids under controlled conditions by observing the effect of different salinities on the growth and survival of the juveniles. Several of the teredinids were seen to grow in salinities in the aquarium which were outside the salinity range in which they were found in the estuary; and early larval development to the umbo-shaped veliger stage was seen in two larviparous species in salinities lower than that in which the adults occurred in the field. From these observations it would appear that the salinity tolerances of the adults, and possibly the pre-settlement larvae, are not the most important factors limiting teredinid distribution in an estuary.

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